Many drugs can be administered through the oral route as liquids, capsules or tablets. As oral administration is a safe, convenient and cost effective route, it is the route taken for most therapeutics. However oral administration has several limitations. Orally administered drugs bypass the mouth and the stomach in order to be absorbed into the system for use. Drug absorption can begin in the mouth and stomach, and can be finally absorbed by the small intestine, passing the intestinal walls, passing through the liver for processing, and then finally be transported through the bloodstream to reach its target site. As such, the drugs can be metabolized before the blood and plasma are reached.
Drugs can be metabolized by oxidation, reduction, hydrolysis, conjugation, condensation and other additional processes that can make the drug easier for a subject to excrete. Some drugs can be metabolized so rapidly that a therapeutically effective concentration in the blood is not reached.
A property of orally administered drugs that can affect its ability to reach its destined tissue or site of treatment can be its absorption and solubility. Solubility behavior is a challenge for many drugs, which can require pharmaceutical formulations with solubility enhancers in order to improve its ability to become absorbed by a system for use. Solubility is a phenomenon of dissolution of solute into a solvent to give a homogenous system and is important for achieving a desired concentration of drug in a systemic circulation for a desired pharmacological response. The solubility of a drug is intrinsically related to its size and its properties. Low aqueous solubility is a problem for many drugs, as a drug will need to be in a form of a solution at the site of absorption, such as within the gastro-intestinal tract. To date, more than 40% of chemical entities developed for the pharmaceutical industry are poorly soluble in water. Solubility however can be increased by the drug solutions of oil in water emulsion, addition of a hydrophilic carrier, cellulosic derivatives, lipids, phospholipids and antioxidants. As such, methods are needed to increase the bioavailability of a drug, such as methods to slow the metabolism of a drug and increase solubility of a drug, in a subject in need is needed.